This invention relates to thin cemented refractory metal carbide articles having uneroded formed surfaces, and also relates to thin flexible unsintered articles of carbide and cementing metal articles suspended in an organic matrix and to a laminating process for producing such sintered and unsintered articles.
Copending patent applications Ser. No. 488,727, filed July 15, 1974 and Ser. No. 418,397, filed Nov. 23, 1973, both assigned to the present assignee, described techniques for producing thin flexible sheets of metal carbide and binder metal suspended in an organic matrix by tape casting a slurry of the ingredients in a solvent, which flexible tapes may be subsequently formed into thin cemented carbide articles by shaping and firing. Since in general it is difficult to achieve cemented carbide articles in thicknesses less than about 1/8 inch by conventional pressing and sintering techniques, the above tape casting techniques are significant in that they enable the production of articles less than 1/8 inch in thickness directly without the necessity for extensive grinding or milling operations to obtain desired small thicknesses.
However, there is an upper limit to tape cast thicknesses obtainable by these techniques of about 0.040 inches. One method employed in the ceramics industry to produce article thicknesses greater than those obtainable by tape casting is to laminate two or more tape cast layers, for example by hot pressing or calendaring through rollers. A multi-laminating technique is described for example; in U.S. Pat. No. 3,725,186. However, such techniques in general result in poor bonding between the layers and in extreme cases result in delamination.
U.S. Pat. No. 3,695,960 discloses a method for improving such bonding between two tape cast layers by bringing the smooth bottom casting surfaces of these two layers into mutual contact prior to lamination and firing. While this technique has been found to improve bonding between tape cast carbide layers, nevertheless where it is desired to form laminates of more than two layers, the obvious problem arises that insufficient smooth casting surfaces are available to achieve mutual contact of smooth surfaces at each layer interface, so that in multi-layer laminates only the casting surfaces of alternate layers can be in contact, giving rise to poor bonding or delamination between adjacent layers.